A railway overload and unbalanced load detection device is an equipment which automatically carries out continuous and dynamic metering and vehicle identification on a moving train without parking or unhooking. Overload and unbalanced load detection equipment used on a railway in China generally utilizes a pressure sensor to serve as a primary instrument for weighing and metering and takes a shear force sensor as an axle counting primary instrument for carrying out vehicle identification. For the railway overload and unbalanced load equipment, having requirement on absolute accuracy of the shear force sensor arranged on a steel rail, a traditional steel rail shear force sensor 9 (FIG. 2) is configured by gluing a strain gauge 10 (FIG. 1) in a conical elastic carrier, so that the traditional steel rail shear force sensor n be fastened by virtue of a bolt only by drilling a hole on a rail web 2 of the steel rail and can sense stress and deformation of the steel rail. A structural diagram and signal outputs of the traditional steel rail shear force sensor 9 are shown in FIGS. 1-5. Principle of an output circuit of the traditional steel rail shear force sensor 9 is shown in FIG. 3, a shear force waveform curve output by the traditional steel rail shear force sensor is shown in FIG. 5, by virtue of the detection mode, the obtained waveform curve meets detection analysis requirement of an overload and unbalanced load detection system, however, the traditional steel rail shear force sensor has insurmountable fatal defects due to the principle and structure thereof:
1. It is required to be drilled in the middle part of the rail web 2 of the steel rail, thereby reducing the rail strength, which is a present situation resolutely against by a railway works department and that needs to be accepted due to work demand and limitation by technical conditions;
2. Due to difference of the steel rail and the shear force sensor in expansion shrinkage coefficients of materials, difference in machining processes and bolt fastening degrees, and vibration influence caused by movement, the traditional shear force sensor 9 has unstable stress state;
3. Adhesive strain gauge 10 sealed form has the same processing technology, limited life, quality differences and higher price with the pressure sensor;
4. With the strain gauge 10 served as one arm of an electronic bridge, additional error factors are added to an output signal of the electronic bridge;
5. Analog output weakens the signal, which needs to be conditioned by subsequent equipment, and it is short in transmission distance and weak in anti-interference capability.